Teaching is the general word for the imparting of knowledge .... Instruction has the imparting of knowledge for its object, but emphasizes, more than teaching, the employment of orderly arrangement in the things taught. [Century Dictionary]

Meaning "an authoritative direction telling someone what to do; a document giving such directions," is early 15c. Related: Instructions.

The word in other Germanic languages also is from French. In English the meaning "a means, an agency" is from mid-14c. The sense of "hand-tool, implement, utensil, something used to produce a mechanical effect" is from early 14c. "Now usually distinguished from a tool, as being used for more delicate work or for artistic or scientific purposes" [OED]. The legal meaning "written document by which formal expression is given to a legal act" is from early 15c. Formerly also used of body parts or organs with special functions.

In wyfhode I wol vse myn Instrument As frely as my makere hath it sent. [Chaucer, "Wife of Bath's Prologue"]

late 14c., "of the nature of an instrument, serving as a means to an end," from Old French instrumental, from Medieval Latin *instrumentalis, from Latin instrumentum "a tool, apparatus" (see instrument (n.)). Meaning "serviceable, useful" is from c. 1600. Of music, c. 1500; noun meaning "musical composition for instruments only" is attested by 1940. Related: Instrumentally; instrumentality.

1520s, from Old French insufficience and directly from Late Latin insufficientia "insufficience," abstract noun from insufficientem "insufficient" (see insufficient). Insufficience "deficiency" is from early 15c.

late 14c., from Old French insufficient (14c.) or directly from Late Latin insufficientem (nominative insufficiens) "not sufficient," from in- "not, opposite of" (see in- (1)) + sufficientem (see sufficient). Originally of persons, "inadequate, unable;" of things, "lacking in what is necessary or required," from late 15c. Related: Insufficiently.

1610s, "of or pertaining to an island," from Late Latin insularis "of or belonging to an island," from Latin insula "island" (see isle). Metaphoric sense "narrow, prejudiced" is from 1775, from notion of being isolated and cut off from intercourse with other nations or people (an image that naturally suggested itself in Great Britain). The earlier adjective in the literal sense was insulan (mid-15c.), from Latin insulanus.

1755, "narrowness of feelings," from insular in the metaphoric sense + -ity. Sense of "state of being an island" (from the classical sense) attested from 1784, in reference to explorations of Australia and New Zealand.

1530s, "make into an island," from Late Latin insulatus "made like an island," from insula "island" (see isle). Sense of "place in an isolated situation, cause (someone or something) to be detached from surroundings" is from 1785. Electrical/chemical sense of "block from electricity or heat" (by interposition of a non-conductor) is from 1742. Related: Insulated; insulating.

noun of action from insulate (v.) in its various senses. From 1767 as "a blocking from electricity or heat" (by interposition of a non-conductor). Sense of "state or action of being detached from others" is from 1798. Literal meaning "act of making (land) into an island" is from 1784; that of "state of being an island" is from 1799. The concrete sense of "insulating material" is recorded by 1870.

1922 (earlier insuline, 1914), coined in English from Latin insula "island" (see isle and compare insula); so called because the hormone is secreted by the islets of Langerhans in the pancreas. Insuline was coined independently in French in 1909.

The particular commercial senses of "make safe against loss by payment of premiums; undertake to ensure against loss, etc." are from mid-17c. (replacing assure in that meaning). Related: Insured; insuring.

1630s, "incapable of being touched," from French intangible (c. 1500) or directly from Medieval Latin intangibilis, from in- "not" (see in- (1)) + Late Latin tangibilis "that may be touched" (see tangible). Figurative sense of "that cannot be grasped by the mind" is from 1880. Noun meaning "anything intangible" is from 1909. Related: Intangibly.